Boundless hits its CHK limit

Boundless Bio went public in 2024 on the promise of CHK1 inhibition, but the company admitted defeat with this mechanism on Tuesday. Boundless is discontinuing the phase 1 Potentiate trial, which had been testing Boundless’s CHK1 inhibitor BBI-355 alongside its RNR inhibitor BBI-825 in oncogene-amplified cancers. The company put the decision down to “market considerations” as well as clinical data; it didn’t provide any results, but things haven’t looked good since May, when the group discontinued BBI-355 monotherapy in Potentiate, citing a “narrow therapeutic index”, as well as ditching combinations with Tarceva and Lytgobi. Boundless had previously abandoned the Starmap trial of BBI-825 due to a “lack of dose-proportional pharmacokinetic exposure”. In another recent setback for the field, Acrivon last week reported disappointing data with its CHK1/2 inhibitor prexasertib in endometrial cancer, but that group is persevering. Prexasertib originated at Lilly; the big pharma also offloaded a CHK1 blocker, LY2880070, to Esperas. Other groups to exit the space include Merck & Co, AstraZeneca and Roche, although plenty of small biotechs remain. Boundless, meanwhile, is switching focus to an oral kinesin degrader, BBI-940, which is set to hit the clinic this half.

Boundless Bio’s pipeline

Source: Company releases.